Colors are of great importance in the way of life of the modern human being. Color is an important factor in the production of various materials and a very central factor in the commercial success of many products. For example, the colors used in packing materials have a very significant function in invoking the interest of consumers and in recognizing brands and trademarks. Colors, for example, help a consumer to find brand name products they are already familiar with among other competing products.
When developing color production methods, the aim is thus to provide very brilliant and exact color effects, which must also be reproducible on different materials and in different processes. Brilliant refers herein to, for example, that the color is very pure, exactly of the desired hue, and bright.
In the conventional so-called subtractive color systems colors are formed by mixing colorants or pigments in certain proportions, in which case a surface treated with this kind of colorants reflects the desired color. This type of subtractive and thus light-absorption-based mixing used on printed matter does not, however, in a known manner provide as brilliant and bright colors as the so-called additive mixing, in which light typically representing three primary colors is directly mixed together. Additive color formation is utilized, for example, in cathode ray tubes, in which the primary colors mixed together in a RGB system are red (R), green (G) and blue (B). In the subtractive color systems used with printed matter, the so-called CMYK system is generally used, in which the primary colors are cyan (C), purple (M), yellow (Y) and black (K).
It is known as such that the color spectrum, i.e. the so-called color gamut formed by the primary colors used in subtractive mixing is smaller than the colors achieved with additive mixing.
From prior art are also known such subtractive printing ink systems, in which more than four primary colors are used to provide a wider color spectrum. One such color system based on six primary colors is described in the U.S. Pat. No. 5,734,800.
Also, it is known as such in additive color systems to utilize more than three primary colors in order to achieve a better color fidelity. From prior art are these days known the so-called multi-color primary displays, in which in contrast with a conventional RGB system, for example, six primary colors are used.
In packing materials color formation has, however, conventionally been based almost solely on subtractive mixing of primary colors for the obvious reason that this type of colors can be easily produced in practice by means of printing methods. The tendency for more impressive color effects has, however, lead to that various hologram-based methods have been developed, in which the colors are produced by means of diffractive elements. By means of the hologram effects, the packing materials are provided with the desired brilliancy and they can, in addition, be used to show the originality of the product, for example, because the implementation of holograms is clearly more demanding than normal printing technique, which thus complicates the production of product copies.
U.S. Pat. No. 5,797,632 discloses a solution, in which a color image is produced on the surface of a substrate by printing ink on the surface, to which ink functioning as a medium are further formed three different color halftone images. These halftone images are formed to the printing ink as diffractive elements reflecting three different primary colors, which diffractive elements produce from said three primary colors a color image based on additive color mixing. The printing ink can be heat-setting, photopolymeric or some other thermoplastic ink (see U.S. Pat. No. 5,797,632 column 6 lines 63 to 67).
Even though the above-mentioned patent U.S. Pat. No. 5,797,632 presents a solution that enables the production of holographic effects that are more brilliant than prior art by means of printing technique on, for example the surface of a packing material, the color spectrum implemented by means of it is, however, still too limited to meet the present and ever-growing needs of, for example, product designers.
As a clear deficiency in the solutions according to prior art can also be noticed that thus far no proper tools have existed either, by means of which tools the color hues of standardized color coordinates, such as the CIE 1931 color coordinates (Commission Internationale de l'Eclairage) could be produced in a controlled manner by means of diffractive components by using additive color mixing. This prevents the wide and effective use of diffractively produced color effects, for example, when designing and producing product packages.